Connection Types for Dummies!

Some of the most common questions that arise on these forums relate to how to connect the various components of your system together and what are the best types of connection to use.

The following is intended to be a basic overview of the types of connection available and their characteristics.

In increasing order of quality, the basic types are as follows:

Type: RFDescription: Carries all video and audio signals on one channelConnectors: F typeAudio: YesComments: Should only be used from the wall socket (or aerial source) to your tuner.

Type: Composite (CVBS)Description: Carries all video on a single channel.Connectors: RCA, BNC, SCART (see FAQ below)Audio: NoComments: Most commonly found as a yellow RCA lead with two attached RCA leads (red and white) for audio.

Description: RGB type signals break up the picture into 5 components; 3 colours and two synchronisation (sync) signals for analogue systems or it keeps the signal as a fully digital stream.NB: You will need an RGB type connection to support a High Definition (HD) digital signal

Type: RGBSDescription: An analogue RGB signal carried over 4 channelsConnectors: RCA, BNC, SCARTAudio: NoComments: Similar to YUV but separates the sync component onto a separate channel and is commonly found on European derived components.

Type: RGBHVDescription: An analogue RGB signal carried over 5 channelsConnectors: RCA, BNC, VGA (Dsub15)Audio: NoComments: Used most commonly by computers for graphics connections. Becoming more common on some plasma and LCD screens.

Type: DVIDescription: Fully digital RGB signal transmission.Connectors: DVI-I, DVI-DAudio: NoComments: Allows the video to be kept in a digital format rather than being converted to analogue then back to digital resulting in a better picture quality. Nb: DVI-A carries a RGBHV analogue signal via a DVI style connector; make sure you source and screen both support DVI-D formats to get digital signal transmission.

Type: HDMIDescription: Fully digital RGB signal transmission with audio. Connectors: HDMIAudio: Yes (digital)Comments: Allows the video to be kept in a digital format rather than being converted to analogue then back to digital resulting in a better picture quality. Also carries audio and supports HDCP (see FAQ below)

Audio Connections:

As most of the above connection types only carry video, you will also have to make an audio connection. Most output sources; Set top boxes (STB), Personal Video Recorders (PVR), DVD players, etc have a separate audio output which come in a range of forms. These may be connected either directly to your screen or to an Amplifier or Surround Sound System.

They come in three basic forms:

Type: Audio outDescription: 2 or more channels carrying analogue audio signals, sometimes with surround sound encoding.Connectors: RCAComments: Most commonly found as two RCA connectors (red and white) that also carry a surround sound encoding, your receiver/amplifier must have a Dolby decoder to separate the surround sound signal. Also found as multiple RCA connectors (6 or more) to carry each channel separately.

Type: Optical outDescription: Fibre optic version of S/PDIFConnectors: ToslinkComments: Capable of carrying all Surround sound transport standards. Needs to be connected to a suitably equipped amplifier to decode the signal.

Frequently Asked Questions:

What is HDCP?

High Definition Content Protection (HDCP) is a new industry standard of copy protection for HD material. It is only supported by HDMI (all) and DVI (some) connections. If material you are viewing is HDCP encoded and if you do not have this carried by a HDMI connection and/or your screen is not HDCP compliant then the picture quality will be downgraded. This is only true if the source unit (STB, PVR, DVD player, etc) is also HDCP compliant. At this time there is very little HDCP encoded material around but this will change over the coming years.It is prudent to consider whether a product you are likely to buy is going to be interacting with HDCP material and if it is HDCP compliant.

What is a SCART connector?

A SCART connector is a 21 pin rectangular shaped connector found on many audiovisual units. It is a European standard connector capable of carrying multiple signal types including; composite, S-video, YUV, RGBS and Audio. There are a range of different types of SCART connection and composite, S-video and audio are directional depending on the application.

What type of connections should I use for each component?

Generally, you should use the best component with the best connection.Eg. HD STB with HDMI or DVI, then DVD player with Component (YUV), then VCR with S-video and so on…However this may be varied if there is a lower quality output that you spend the majority of the time viewing. It is normally best to try out various components on each input type and find the combination that you are happiest with.

My amplifier has multiple component inputs and a single output, should I run everything through the amp?

While this makes changing the viewing source easier, it can, depending on the quality of the amplifier, reduce the quality of the signal to the screen. The best quality of picture is obtained by sending the image directly from the source to the screen.

My STB/PVR outputs the picture with one type of connector but the screen has a different type, what can I do?

There are adapters (cable and plug type) that will allow you to change the connection type but they will only pass through the signal type being supplied.

My STB/PVR outputs one type of RGB signal but the screen accepts another, what can I do?

The most common of these situations is when your STB/PVR outputs RGBS but the screen will only accept YUV or VGA (RGBHV). In this case you will have to get a powered converter box that will convert the signal to the desired type. These are readily available for between $130 and $160. This will provide a much better picture than stepping down to the S-video or composite connection, and can support HD pictures.

Peter, congrats on this piece of work. Very well done indeed. Would certainly saves a lot of newbies having to search round the forum to their queries on connectivities. This post would have certainly saved me a lot of angst when I first started out...

S-Video is essentially a composite analog signal separated into two cables. One is the monochrome signal called luminance or Y(black, grey and white) and a colouring signal called chroma called C. These signals have a similar quality to composite, except that in areas of fine black and white patterning which is just off vertical will not become coloured in an obvious pattern. Typical of some suits, striped shirts etc.

Since this and dot patterning on strong colours does not need to be removed allows sharper vertical edges in the picture.

S-Video also comes in PAL and NTSC. This means that S Video can never convey High Definition pictures.

High Definition picture standards specify stronger colours in the display device for the primary colours of red, green and blue. This will give a greater colour range. The camera needs to use colour filtering and encoding to match. This produces a Luminance (Y) and a pair of colouring signals (Pr) and (Pb).

Standard Definition picture standards including PAL analog produce from the camera Y, Cr and Cb signals. These are then conveyed to the display for display with the coloured primaries, which we are used to.

Y, U, V are used in PAL coding and are incorrect names in digital signals and Y, Cr & Cb should be used instead.

North American & Japanese Signals.

Analog signals are called NTSC (Never Twice the Same Colour) is a less sharp image than we have, (702 x 480 pixels) however the flicker at high brightness is less and motion is a little smoother.

The colouring signal is converted to a frequency of 3.8 MHz. Usually to make it showable on Australian TVs, this frequency is converted to approximately 4.43 MHz which is used for PAL

DVDs are digital and are recorded as standard definition using a Y, Cr & Cb signal. This signal should be used for replay not NTSC 4.43 which is of poorer quality.

Connecting Digital TV equipment (STBs, PVRs, DVDs)

For all systems it is assumed that there is no amplification or loss between the camera and the display device. So white is +700 mV (digital level 240 out of 256 levels) at the camera output for Red, Green and Blue signals, as is the Y signal. This is what the display needs to display white.

So intermediate equipment such as STBs, PVRs and DVDs must also produce a +700 mV or digital level 240.

DVDs are all currently standard definition so the outputs (except composite and S-Video) are either Y, Cr & Cb.If this signal is fed into an SD display device then every thing is fine. If it is fed into an HD display the display can recognise the difference between an SD and an HD (Y, Pr & Pb) signal. So if the Y, Cr & Cb signal is fed into an HD display it will display it correctly for that signal.

HD compatible SD display will display an Y, Pr & Pb the image but very strong colours will be incorrectly displayed.

The last problem of interconnection is with North American (Zone 1 DVD)These are recorded at 30 frame/s (60 field/s). The rest of the world is 25 frame/s and film is 24 frame/s.

When these DVDs and videos are shown, the display must be able to show these frame or field frequencies otherwise the picture will roll continuously.

For ReferenceWith the exception of HDTV the luminance signals (Y) use the same proportions of red, green and blue signals (RGB) to produce a "black & white" signal.

The important point is the weighting factors in the colouring in signals which determine the hue (the colours of the rainbow) and the saturation (strength of the colour).

The only suggestion I'd make is to add that RGBS is most commonly SCART and stress that the cheap scart to RGB (3xRCA's) adaptors don't work with component inputs on TVs (unless the STB does component over SCART). There's lots of posts on this one!

Also, RGBS is listed as HD capable? I don't think SCART is.

However I think you post is excellent, accurate and succinct. Perhaps keeping it simple is best.

The only suggestion I'd make is to add that RGBS is most commonly SCART and stress that the cheap scart to RGB (3xRCA's) adaptors don't work with component inputs on TVs (unless the STB does component over SCART). There's lots of posts on this one!

Also, RGBS is listed as HD capable? I don't think SCART is.

However I think you post is excellent, accurate and succinct. Perhaps keeping it simple is best.

SCART is capable of carrying a HD signal as it is just a form of connector. It is the output from the device that is what determines whether it is HD capable or not.

For example; Composite or S-video over SCART is not HD capable but Component (YUV) or RGBS over SCART is HD capable.

The reality is that the vast majority of HD outputs now and in the future are supplied through some other form of connector, such as, Component, DVI or HDMI. Further in the future it will likely be the case that the only way to carry a HD signal will be by HDMI. This is the direction the industry is heading anyway....

SCART is capable of carrying a HD signal as it is just a form of connector. It is the output from the device that is what determines whether it is HD capable or not.

For example; Composite or S-video over SCART is not HD capable but Component (YUV) or RGBS over SCART is HD capable.

Yes that's true, but I'm not familiar with any equipment designed to input or output HD over SCART. In any case I wouldn't rate it higher in quality than component. RGBS may be superior to YUV in theory, but in most applications I think YUV is better.

All,I added the bottom part to show that it is just the amount of signal mixtures which change.

The main message is that S-Video cannot carry HD and is only a little betteer than composite.

The best connection is to use a digital one so that there is only one decoding process on the signal and this is in the display, particularly if it is a progressive display.

The next best is to use a component connection so that the recovery of the RGB signals only happens once.

Next best is RGB. This is because in a progressive display the signal is reconverted into a component signal for storage and then reconverted to RGB.

Followed by the poor cousins, S-Video and Composite.

The most important point is that the use of Y, Cr & Cb as compared to Y, Pr & Pb is irrelevant to the user except for the display.

AlanH

Hi,

Surely RGB on D-Sub is better than component though... or are you saying that D-SUB VGA gives a digital signal, as I thought it was analogue still. Also the difference between Y Pb Pr and Y Cb Cr is very relevant on my display, and I'm sure many others. My display displays 576i through composite, s-video, and Y Cb Cr. It only displays 576/720p and 1080i through the Y Pb Pr, D-SUB VGA ports, no 576i. This then functions in a "normal" mode for analogue TV, SD DTV, and 576i DVD playback, but in a "HD" mode for 576/720p, 1080i, and monitor signals for PC's. Si this is very relevant to my display as it has 2 seperate inputs marked accordingly Y Cb Cr and Y Pb Pr.

JSmith,
The reason I am prefering component to RGB is as follows.
The sharpest picture information is in the luminance channel (Y). You cannot detemine colours in fine detail, if they are the brightness. The finer the detail the greater the frequency range required as well as the greatest amount of data.

The following displays store the image:progressive display or for LCD or Plasma display
The signal is supplied in the Luminance (Y) and a pair of colouring signals. You cannot see the colours in fine detail, so for a colour signal the memory required to store this image is twice that required for luminance. If RGB is to be used, then it will be 3 times that of the luminance. So if RGB is used then it has to be converted to luminance and the pair of colouring signals. The image is stored and when it is to be displayed it is converted back to RGB.

So it is better to only converting from component to RGB once. Multiple conversions can cause colour changes.

The VGA connector has RGB analog signals on it otherwise you can only see 8 or 16 colours. DVI connectors come as analog, digital or both. The analog version is RGB. Digital is component, so that the data rate can be kept lower.

To support JSmith, one other aspect regarding Component signals is that all DTV signals are captured, processed, stored, and transmitted in component format, (MPEG 4:2:2 or MPEG 4:2:0 being Y:U:V) it is arguable that presenting the signal to the display device in component format may in most cases have some "signal" advantage over D-SUB RGB, but in practice there is probably little difference.

At the end of the day the difference between the two will depend on the individual STB and the Monitor. In some cases one will be better than the other, but they are both excellent choices, just choose what is best for you based on your available input/output combinations.

To support JSmith, one other aspect regarding Component signals is that all DTV signals are captured, processed, stored, and transmitted in component format, (MPEG 4:2:2 or MPEG 4:2:0 being Y:U:V) it is arguable that presenting the signal to the display device in component format may in most cases have some "signal" advantage over D-SUB RGB, but in practice there is probably little difference.

At the end of the day the difference between the two will depend on the individual STB and the Monitor. In some cases one will be better than the other, but they are both excellent choices, just choose what is best for you based on your available input/output combinations.

That's right.

Given that Component (YUV), RGBs and VGA (RGBHV) are all effectively five channel analogue RGB signals (3 colour and 2 sync) there should be little diference between the final PQ.

You would only expect the VGA to provide a better picture where the screen's onboard processor is of a lower standard and hence less capable at seperating the sync channels in YUV and RGBs.

Most modern screens should have no problems with this though.......

The bottom line is to try different formats with your own equipment to see what works best for your system and it's own components. What works for one person is not necessarily going to work best for someone else using different components.

The other issue worth mentioning here is cable length. The theoretical advantages of one format over another can be negated by long cables that are of incorrect impedance, poor shielding, or result in significant signal loss.

So while, say, Scart may be equal to component on a short run, component via cheap RG6 may be better for that 10m run to your PJ.

This can be a bit of a trap, because while it's easy to test short runs with a few different cables it's harder to get a 10-20m run to try, and the results over 10+m will be different to that 1m VGA you borrowed off the computer.

My advice for long runs is to learn from the experience of other forum members who have seen what actually works.

peter vfr,
How can the RGB be better than component? That is how the signal is delivered to your home. Are you going to invent more detail, and more accurate colour? The best result is to convert to RGB once in the display. This minimises DAC/ADC and matrix coefficent changes.

How can the RGB be better than component? That is how the signal is delivered to your home. Are you going to invent more detail, and more accurate colour? The best result is to convert to RGB once in the display. This minimises DAC/ADC and matrix coefficent changes.

Ultimately there should be very little difference between YUV, RGBs and RGBHV.

These are each only variations of sending a colour seperated signal in analogue format to your screen. Different combinations of components will give different results so just use whichever works best for your system.

I've been learning quite a bit last few days reading your posts. Could anyone suggest me books or good sites where I can learn more about digital audio and video technical stuff like the ones you've been discussing in the forums? Not pos-productions and editing but the electronic side of it...

New to this forum, I currently live in the UK and may be coming over to wonderful Perth to live there. I have a Panasonic 42 inch High Definition Plasma IDTV, will I be able to receive the digital broadcasts on this tv in Australia. I ask this because ordinary UK CRTVs using the Australian analogue signal do not work.